I got the info directly from Dana Riddle.
""I can say with a high degree of certainty that red wavelengths are detrimental to zooxanthellae pigment content and health. Merely stating that one supplements blue wavelengths (or perhaps others) with red wavelengths raises a number of questions, to wit:
1. Amount of red wavelength supplementation. Exactly how much?Based on what? PAR measurements? (fraught with a high degree of error with inexpensive PAR meters, that is, Apogee meters). Analyses of spectral quality via spectrometer?
2. Length of exposure. Polyp expansion is generally greater during the first few days of exposure to red light. Zooxanthellae have not yet 'realized' that exposure to red light is not a good thing. Generally, the ratio of red light-absorbing pigments is quite high in environments where violet/blue wavelengths are predominant. When exposed to high amounts of red light, the coral (via feedback loop from its symbionts) recognizes red light as a good thing. However, since the photopigments are ramped up to absorb red light, the situation becomes one of too much of a good thing.
3. Understanding of the dia/dino xanthophyll cycle. Dynamic photoinhibition involves certain xanthophylls. These photopigments absorb only blue blue and shunt the absorbed energy away from photosystems. This natural 'pressure relief' valve for photosynthesis works only with blue wavelengths - and why shouldn't it? Corals/zooxanthellae are normally and naturally exposed to those wavelengths skewed towards violet/blue/blue-green wavelengths.
Dr. Kinzie published his experiments with red light and zooxanthellae in the late 20th century. He realized red light was a regulating mechanism for either the number of zooxanthellae and/or the content of their photopigments (chlorophlly a, c2, peridinin, etc.). In laymen's terms, this regulation is referred to 'bleaching'. Jokiel was a co-author and or reviewer of Kinzie's work. When I discussed this with him recently and within the context of our understanding of chronic/dynamic photoinhibition, he was quite excited by this new perspective. In addition, other peer-reviewed works have confirmed coral growth is greatest when corals are maintained in conditions of deficient (natural) amounts of red light."
